Make more threading improvements

- ASAN memory morgue is now lockless
- Make C11 atomics header more portable
- Rewrote pthread keys support to be lockless
- Simplify Python's unicode table unpacking code
- Make crash report write(2) closer to being atomic
- Make it possible to strace/ftrace a single thread
- ASAN now checks nul-terminated strings fast and properly
- Windows fork() now restores TLS memory of calling thread

libc/intrin/wsarecv.c

@@ -52,7 +52,7 @@ textwindows int WSARecv(
   if (rc == -1) {
     __winerr();
   }
-  if (UNLIKELY(__strace > 0)) {
+  if (UNLIKELY(__strace > 0) && strace_enabled(0) > 0) {
     kprintf(STRACE_PROLOGUE "WSARecv(%lu, [", s);
     DescribeIovNt(inout_lpBuffers, dwBufferCount,
                   rc != -1 ? NumberOfBytesRecvd : 0);